(1) Field of the Invention
This invention relates to an improved catalyst component for the polymerization of olefins and a catalyst therefor which are capable of providing high polymerization activity per unit weight of the catalyst component and high yield of stereoregular polymer when applied to the polymerization of olefins, and more particularly relates to a catalyst component obtained by contacting a fatty acid salt of magnesium, a carbonate of magnesium or a substance containing said carbonate, diester of an aromatic dicarboxylic acid and a titanium halide, and to a catalyst therefor comprising the catalyst component, a silicon compound and an organoaluminium compound, where polymerization includes homopolymerization and copolymerization thereof.
(2) Description of the Prior Art
A catalyst for the polymerization of olefins formed by combining a solid titanium halide as a catalyst component with an organoaluminium compound is well known in the art. However, in the polymerization of olefins by use of the conventional catalyst, the yield of polymer per unit weight of the catalyst component or of titanium moiety in the catalyst component (hereinafter referred to simply as a polymerization activity per unit weight of the catalyst component or of titanium) is so low that the so-called deashing process for subsequently removing catalyst residues from the produced polymer is indispensable in order to obtain an industrially applicable polymer. In the deashing process, alcohols or chelating agents are used in large amounts, so that the deashing process needs an apparatus for recovery thereof as well as the deashing apparatus itself, and consequently has many problems accompanying therewith relative to resources, energy, and the like. Thus, the deashing process raises great problems to be solved urgently in the art. A number of studies and suggestions have been made for enhancing the polymerization activity per unit weight of titanium in the catalyst component, so that the complicated deashing process may be dispensed with.
Especially as a recent tendency, a large number of suggestions have been made such that the polymerization activity per unit weight of titanium in the catalyst component is remarkably enhanced in the polymerization of olefins with a catalyst component prepared by supporting a transition-metal compound as an active ingredient such as a titanium halide on a carrier material so that the active ingredient may act effectively.
However, the prior art employing magnesium chloride as the carrier as described above, has such a disadvantage that the chlorine moiety contained in the magnesium chloride conventionally used as the carrier has an adverse effect on the produced polymer, resulting in leaving problems to be solved such as requirements for such a high activity as to be substantially free from the adverse effect due to the chlorine moiety, or as requirements for controlling a concentration of the magnesium chloride itself at a sufficiently low level.
The present inventors proposed a process for preparing a catalyst component for the polymerization of olefins in Japanese Patent Laid-Open Application No. 204004/1983 for an object of reducing a chlorine content in the produced polymer with high polymerization activity and high yield of stereoregular polymer, attaining the aforementioned object. The aforesaid Japanese Patent Laid-Open Application No. 204004/1983 discloses a process for the preparation of catalyst component for the polymerization of olefins which process comprises contacting (a) a fatty acid salt of magnesium, (b) an electron donor compound, (c) a titanium halide of the general formula: TiX.sub.4, wherein X represents a halogen atom, and a carbonate of magnesium or a substance containing said carbonate. Although the aforesaid Japanese Patent Laid-Open Application No. 204004/1983 further discloses that the electron donor compound preferably includes ethyl benzoate, ethyl p-anisate and ethyl p-toluate, said Japanese Patent Laid-Open Application No. 204004/1983 teaches nothing about the use of the diester of the aromatic dicarboxylic acid as used in the present invention. The aforesaid Japanese Patent Laid-Open Application No. 204004/1983 also discloses the use of only ethyl p-toluate as an electron donor compound on polymerization as shown in Examples, but teaches nothing about the use of the silicon compound used in the present invention on polymerization. Moreover, the catalyst component obtained by the process of Japanese Patent Laid-Open Application No. 204004/1983 is not satisfactory in improvements of polymerization activity per unit weight of the catalyst component and of yield of stereoregular polymer, and in reduction of chlorine content in the produced polymer, development of a catalyst having improved catalyst performances having been demanded in the art. Further, it is essential for a catalyst formed by combining a catalyst component using magnesium chloride as a carrier with an organoaluminium compound to carry out on an industrial scale the polymerization of olefins, especially stereoregular polymerization of propylene, 1-butene, and the like in the presence of an electron donor compound such as aromatic carboxylic acid esters in the polymerization system. However, the aforementioned aromatic carboxylic acid ester imparts a peculiar estereal odor to the produced polymer and the amount thereof is increased to a relatively large amount when polymerization is carried out in the presence thereof, raising a serious problem of deodorizing therefrom in the art.
It was substantially impossible for the so-called highly active supported catalyst formed by use of a catalyst component employing the aforementioned magnesium chloride as a carrier to be of practical use, because use of the supported catalyst results in abrupt deactivation thereof in spite of high activity thereof in the beginning of polymerization, and results in raising problems in process operations, particularly in the case where a prolonged polymerization time is required as in block copolymerization and the like. In order to solve the aforementioned problems, Japanese Patent Laid-Open Publication No. 94590/1979 discloses a catalyst for the polymerization of olefins which comprises a catalyst component prepared by use of magnesium dihalide as one of the starting materials, an organoaluminium compound, an aromatic carboxylic acid ester, and a compound having a M--O--R group. However, the catalyst disclosed as above fails to solve the problem of deodorizing from the produced polymer in that organic carboxylic acid esters are used on polymerization, and requires complicated procedures for the preparation thereof with practically insufficient catalyst performance and polymerization activity with time.
In order to solve the aforesaid problem, the present inventors have proposed a novel catalyst component and catalyst. The catalyst for the polymerization of olefins comprises: (A) a catalyst component obtained by a process comprising contacting (a) a fatty acid salt of magnesium and (b) a dialkoxymagnesium, (c) mono or diester of an aromatic dicarboxylic acid, (d) a halogenated hydrocarbon, and (e) a titanium halide of the general formula: TiX.sub.4, wherein X represents a halogen atom, (B) a silicon compound represented by the general formula: SiR.sub.m (OR').sub.4-m, wherein R is hydrogen, alkyl group or aryl group, R' is alkyl group or aryl group, and m is represented as 0.ltoreq.m.ltoreq.4, and (C) an organoaluminium compound.
In addition to the aforesaid problems in the prior art, need for providing a catalyst which is capable of providing a polymer having narrow particle size distribution and high bulk density, as well as uniform particle shape has recently been increased in the art. The catalyst component and catalyst described above by the present inventors. have excellent performances including a prolonged polymerization activity with time, but are not satisfactory to meet the aforesaid needs in the art. The aforesaid uniformness in the particle size and shape of the produced polymer provides such advantages in the art as to make it easy to handle the produced polymer and to make it possible to omit the pelletizing step, and particularly has a great importance taking into consideration the application of the catalyst having uniform particle size and shape to the gas phase polymerization to which attention has recently been made in the art.